Terpenoids or terpenes represent a family of natural products found in all organisms (bacteria, fungi, animals, plants) and these compounds are made up of five carbon units called isoprene units, which are classified by the number of units present in their structure. Thus, monoterpenes, sesquiterpenes and diterpenes are terpenes containing 10, 15 and 20 carbon atoms respectively. The common five-carbon precursor to all terpenes is isopentenyl pyrophosphate (IPP). IPP forms the acyclic prenyl pyrophosphate terpene precursors for each class of terpenes, e.g. farnesyl-pyrophosphate (FPP) for the sesquiterpenes, and geranylgeranyl-pyrophosphate (GGPP) for the diterpenes. These precursors serve as substrate for the terpene synthatases or cyclases, which are specific for each subclass of terpene, e.g. monoterpene, sesquiterpene or diterpene synthases. Some terpene synthases produce a single product, but most of them produce multiple products. The synthases are responsible for the extremely large number of terpene skeletons. Finally, in the last stage of terpenoid biosynthesis, the terpene molecules may undergo several steps of secondary enzymatic transformations such as hydroxylations, isomerisations, oxido-reductions or acylations, leading to the tens of thousand of different terpene molecules.
Patchoulol and β-santalene are classified as sesquiterpenes whereas sclareol is classified as a diterpene.
The biosynthesis of terpenes in plants has been extensively studied and heterologous expression, in vivo, and in vitro testing are important tools when characterizing genes involved in terpenes biosynthesis. Until now, most plant genes encoding isoprenoid biosynthetic synthases have been characterized using bacterial, yeast, or insect cell-based expression systems [1,2]. However, synthase activity is highly dependent on the assay conditions and choice of heterologous expression hosts. For example, it has been demonstrated that acidification of the yeast growth media led to rearrangement of enzymatic products [2]. Similarly, a diterpene synthase from Norway spruce was shown to be a multi-product synthase when purified and characterized in vitro, but when expressed in yeast and characterized in vivo only a single product accumulated [3, 4]. It was also recently shown that a monoterpene synthase from sweet basil generated different product profiles when characterized using microbial systems compared to in planta characterization [5]. Hence, the biochemical function of a plant synthatase expressed in bacterial or fungal hosts may differ from the endogenous in planta function.
U.S. Pat. No. 8,058,046 relates to sesquiterpene synthases derived from patchouli plants, and methods of their production in suitable host cells such prokaryotes, yeast or higher eukaryotic cells. U.S. Pat. No. 8,058,046 provides nucleic acid molecules identified in Pogostemon cablin comprising a nucleotide sequence that encodes for at least one sesquiterpene synthase, which may be used to convert e.g. farnesyl-pyrophosphate (FPP) to various sesquiterpenes, including patchoulol. U.S. Pat. No. 8,058,046 exemplifies the expression of sesquiterpene synthases from patchouli plants in bacteria, E. coli. 
US20110281257 relates to sesquiterpene synthases derived from Santalum species, and methods of their production in suitable host cells such prokaryotes, yeast or higher eukaryotic cells. US20110281257 exemplifies expression of sesquiterpene synthases from Santalum species in at least S. cerevisiae. US20110281257 provides nucleic acid molecules and variants thereof comprising a nucleotide sequence that encodes for at least one sesquiterpene synthase, which may be used to convert e.g. farnesyl-pyrophosphate (FPP) to various sesquiterpenes including β-santalene.
Genes encoding diterpene synthases have been identified and cloned and the corresponding recombinant enzymes characterized. Amongst other, US2011041218 relates to sclareol synthases, a diterpeniod, from Salvia sclarea species, and methods of their production in suitable host cells such as prokaryotes, yeast or higher eukaryotic cells. US2011041218 exemplifies expression of the diterpene synthases from Salvia sclarea in at least S. cerevisiae. US2011041218 provides nucleic acid molecules and variants thereof comprising a nucleotide sequence that encodes for various diterpene synthases, which may be used to convert e.g. geranylgeranyl-pyrophosphate (GGPP) to prepare sclareol. US2011041218 describes amongst other two synthases wherein GGPP is first converted to labdenediol diphosphate (LPP) and then converted to sclareol.
US20100297722 relates to the provision of compositions and processes for production of terpenoids from transgenic moss cells. US 20100297722 specifically relates to overexpression of various taxadiene synthases having activities towards geranylgeranyl-pyrophosphate and the derivatives thereof to produce different intermediates and end-products of diterpeniod compounds. In particular, expression or overexpression of specific polypeptides in Physcomitrella patens resulting in the production of terpenoid compounds such as various substituted taxadienes, 10-deacetylbaccatin III, abietadiene, abietic acid, steviol, steviolmonoside; stevioside; rebaudioside A, kaurenoic acid, a cembranoid, momilactone A-B, oryzalexins A-F, oryzalexin S and phytocassanes A-E, are exemplified.
Sesquiterpenes and diterpenes, including patchoulol, β-santalene, and sclareol, accumulates in plants and can be extracted by different means such as steam distillation or solvent extraction that produces the so-called essential oil containing the concentrated terpenes. Such natural plant extracts are important components for the flavor and perfumery industry due to their flavour and fragrance properties, and some sesquiterpenes and diterpenes may even possess cosmetic, medicinal and antimicrobial effects. Extracted terpene molecules are often used as such, but in some cases chemical reactions are used to transform the terpenes into even higher valued molecules
Because of the complexity of the terpene structure, production of individual terpene molecules by chemical synthesis is often limited by the cost of the process and may not always be chemically or financially feasible. The price and availability of the plant natural extracts is dependent on the abundance, the oil yield and the geographical origin of the plants. The recent progress in understanding terpene biosynthesis in plants and the use of modern biotechnology techniques opens new opportunities for the production of terpene molecules. Thus, there exist a continuously need to provide improved biological production of terpenes and products derived therefrom, such as patchoulol, sclareol, and β-santalene, at more environmental friendly conditions and/or higher efficiency.